The invention relates to an air intake duct system for internal combustion engines, and in particular for V-engines.
From DE 197 56 332 an air intake duct system is known, wherein the length of a plurality of air intake ducts, each connectable with a cylinder of an internal combustion engine, is continuously variable. For this purpose, the helical intake ducts are arranged side by side. Each helical air intake duct comprises an inlet opening connected with a central inner area of the air intake system, wherein the air enters the helical duct through said inlet opening and, after having passed through the helical duct, is directed to the corresponding cylinder. Inside the central area a tubular duct portion is arranged which defines the inner wall of the helical duct and comprises the air inlet opening. The tubular duct portion is arranged to swivel such that the position of the air inlet opening can be varied. By swivelling the tubular duct portion, the length of the air intake duct, i. e. the distance between the air inlet opening and the air outlet opening to be travelled by the air, is thus continuously variable.
The individual duct portions forming the intake ducts are arranged adjacent to each other or are stacked one upon the other, wherein the air intake ducts are alternately connected with one or the other row of cylinders of the V-engine. For swivelling the inner duct portions said duct portions are connected with a swivelling axis. The air intake ducts connected with a respective side of the V-engine have the same length and are thus jointly operated via a swivelling axis. Therefore the air intake duct system comprises two swivelling axes which are respectively connected with the swivel-mounted duct portions for one or the other row of cylinders of the V-engine. To realize air intake ducts of essentially the same lengths for the individual cylinders, the individual air intake ducts of one or the other row of cylinders are alternately arranged in the air intake duct system. The two swivelling axes are thus connected only with every second swivel-mounted duct portion of the air intake system and only pass through the respective other duct portion.
The swivelling axes are e. g. supported in individual sliding bearing sleeves. The sliding bearing sleeves, which are e. g. made of hardened steel, are arranged in a housing of the air intake duct system or in the stationary duct portions. Provision of individual bearing sleeves for the two swivelling axes has the disadvantage that due to a minimum thickness of the bearing sleeves and the resultant minimum distance of the swivelling axes to each other, the necessary space requirement is relatively large.
Another possibility is to directly support the swivelling axes, which are normally made of metal, in the plastic duct portions. This however results in relatively heavy wear such that the required average service life cannot be reliably attained.
It is an object of the present invention to reduce the space required for the air intake duct system.
According to the invention, the space required for the air intake duct system can be reduced by reducing the distance of the two swivelling axes to each other. Since supporting in a plastic material is disadvantageous because of the wear, the present invention provides a common integral bearing part having two swivelling axis bearings, i. e. one for each of the two swivelling axes. Preferably, two sliding bearing sleeves are provided which overlap each other such that the bearing part has the form of an xe2x80x9c8xe2x80x9d. A partition wall arranged between the two bearing sleeves serves as a sleeve wall for the two bearing sleeves. In contrast to identical bearing sleeves arranged side by side, the two cylindrical sleeves can be arranged considerably more closely to each other in the openings of the bearing part according to the invention such that the accommodation space required is reduced.